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[leetcode] problem 189 – rotate array

admin 11月 13, 2020 0

Given an array, rotate the array to the right by k steps, where k is non-negative.

Example

No.1

Input: [1,2,3,4,5,6,7] and k = 3

Output: [5,6,7,1,2,3,4]

Explanation:
rotate 1 steps to the right: [7,1,2,3,4,5,6]
rotate 2 steps to the right: [6,7,1,2,3,4,5]
rotate 3 steps to the right: [5,6,7,1,2,3,4]

No.2

Input: [-1,-100,3,99] and k = 2

Output: [3,99,-1,-100]

Explanation:
rotate 1 steps to the right: [99,-1,-100,3]
rotate 2 steps to the right: [3,99,-1,-100]

Note

  • Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.
  • Could you do it in-place with O(1) extra space?

Code

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public void (int[] nums, int k) {
    int n = nums.length;
    k %= n;

    reverse(nums, 0, n - k - 1);
    reverse(nums, n - k, n - 1);
    reverse(nums, 0, n - 1);
}

private void reverse(int[] nums, int i, int j) {
    while (i < j) {
        int temp = nums[i];
        nums[i] = nums[j];
        nums[j] = temp;
        i++;
        j--;
    }
}
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